The squirming and tension. Seeing her wonder when the next hit will come.

How fast how hard will it be seeing her prepare. The sound and sight as her cheeks turn red, both sets from the slapping sounds.

The scent of her as she gets more and more turned on as the weight of the hits build. Her moans and whimpers.

As it grows, her moans grow louder, holding off until she whimpers for more, and in confusion, and then the harsh moan as her ass is slapped again.

The heat as it builds in the vicinity and the rush of emotions from her and myself.

anyways, my experience is limited but, that is what i've experienced. Ozme's first post and IDs post sum it up the best however in my opinion